Young-Kee Kim: Research

As an experimental scientist, I am working on particle physics whose goal is to understand how the universe works at
the most fundamental level by discovering and understanding the fundamental constituents (called elementary particles)
and the forces acting among them.

My main physics interest is understanding the orgin of mass for elementary particles (studies of the Higgs
boson), and searching for dark matter and other new physics using the Higgs boson.

ATLAS at the LHC (2010 - ): A new particle, which behaves like the predicted Higgs,
was discovered at mass of 125 GeV by the ATLAS and CMS experiments at the LHC at CERN in 2012 via processes
in which this particle decayed into a pair of photos, Z bosons and W bosons (H → γγ, ZZ, WW). Francois
Englert and Peter Higgs received
the Nobel prize in 2013 for their theoretical discovery of the Higgs mechanism.

The most critical goal at the LHC over the coming years is to develop a deeper understanding of the nature of
the Higgs particle. One key process yet to be observed is where the Higgs decays into a pair of bottom
quarks (H → bb), the most
frequent decay mode for the 125 GeV Higgs. This mode allows to study the Higgs boson's coupling to fermions (such as
electrons and quarks) and to probe directly the mechanism for fermion mass generation via the Higgs. Many
well-motivated new physics models predict significant deviations to the H → bb Standard Model rate. Thus this decay
channel will be a good tool to explore new physics models.

Observing and studying H → bb,
and searching for dark matter particles in the H(→bb) + dark matter
process are my main interests and current activities of my group.
These tasks will require significant improvements of b-jet triggers using the new tracking trigger (FTK) combined with
the LHC accelerator and detector upgrades. In the past few years, my research group (students and postdocs) has been
heavily involved in the FTK (hardware and simulation) that has more capability and flexibility than the current
trigger system. In addition, my group searches for a new vector boson that decays into top and bottom quarks.

CDF at the Tevatron (1990 - 2013):
At CDF experiment, my group measured the masses of the W boson and the top quark very precisely (numerous measurements were made using different decade modes, different datasets and different analysis techniques). These measurements predicted the mass of the Higgs boson (the "core" of the very successful theory of particle physics, the Standard Model, and thought to be key to understanding why elementary particles have mass) to be less than 145 GeV.

My group has also involved other topics measuring the diboson production process whose final states are similar to those of the Higgs boson process (this is an important step for designing Higgs searches), the Bs oscillation, the lifetime of the top quark (by measuring its width), the mass difference between the top and anti-top quarks, properties of the Z and W boson (their production cross section and forward-backward asymmetry), and decay rates of bottom and charm mesons.

Accelerator Physics (2009 - ):
Although accelerator physics is an active research field, and
accelerators are critical for particle physics research
and other research areas in science, the U.S. has not been educating and training enough accelerator students. Thus, I have
been giving some of my time to educating and training students in accelerator physics. The following is the list of
topics and Ph.D. students: